Steroid hormones regulate carbohydrate metabolism, salt and water balance, and reproductive function, and hence are crucial to life. Much is known about the pathways by which steroid hormones are made from cholesterol in the adrenal and gonads; less is known about the enzymes mediating these hormonal transformations, and virtually nothing is known about the regulation of production of these enzymes. Furthermore, while steroid synthesis is classically considered to be confined to the adrenal and gonad, recent data indicate steroidogenesis may occur in other tissues. The enzymes responsible for such "ectopic steroidogenesis" are unknown. The recent cloning of cDNAs for three of these steroidogenic enzymes now permits study of their regulated synthesis at a molecular level. Employing probes for the cholesterol side chain cleavage enzyme (P450scc), 21-hydroxylase (P450c21), and 17-hydroxylase (P450c17), we propose to use in situ hybridization histochemistry to determine the precise cell types responsible for the synthesis of each of these enzymes in a variety of tissues. Hormonal manipulation of intact animals will be done to increase or decrease the production of glucocorticoids, mineralocorticoids or sex steroids selectively. In situ hybridization histochemistry can then identify loci of differential regulation of each of these enzymes. The feasibility of the proposed experiments has already been demonstrated by our preliminary data.